A typical application of such prostheses is mammoplasty by insertion of mammary implants, and the following description will be directed to such an application., it being understood that this description is intended as a non-limiting example.
It is well-known that present mammary prostheses are generally made of a shell comprising flexible silicone film having a spherical shape more or less flattened and filled with a silicone gel, physiological salt solution, or both.
The drawbacks of using silicone filling gel include the risk of gel leakage through the film shell, either by transudation or even by tearing, with local or even general complications.
The drawbacks of using a physiological filling solution also include the risk of leakage either by tearing of the film or at the filling valve. In both cases mentioned above, there are no physiological consequences, but there occurs a decrease in volume unavoidable after some time and always unaesthetic, often requiring a new surgical operation.
To prevent such drawbacks, there have been attempts to use prostheses comprising a central portion made of silicone gel and a peripheral portion filled with physiological solution ostensibly to oppose gel transudation. However, such composite prostheses may suffer from the drawbacks of both above-mentioned devices.
Prostheses have also been more recently proposed comprising means for providing progressive expansion by serial injection of saline solution through a filling valve in-situ over a period of time, to obtain tissue expansion. In addition to the above drawbacks, this recent process involves several interventions in order to obtain a long term implant or to remove the filling valve.
It should also be kept in mind that the insertion of an implant into living tissue may cause spontaneous creation around the implant of an exclusion membrane, which can retract. This is known as "capsular contracture" and in some cases, specifically mammary implants, the formation of such a hard capsule can only be remedied surgically.
Thus, there is still a need to eliminate the above drawbacks, by avoiding the use of silicone gel and aiding in the prevention of leakage or loss of physiological solution from an implant. There also is a further need to provide an opportunity to modify the volume of the implant, at will, without surgical intervention.